The syntax is:
node=AdminControl.getNode()
AdminTask.installBusinessSpaceWidgets('[-nodeName %s -serverName server1 -widgets C:/package/widgets/Widgets.zip]' % node)
Using a real list can be more convenient sometimes:
node=AdminControl.getNode()
AdminTask.installBusinessSpaceWidgets(['-nodeName', node, '-serverName', 'server1', '-widgets', 'C:/package/widgets/Widgets.zip'])